<template>
    <div>
        <h1>当前求和为：{{ sum }}</h1>
        <select v-model.number="n">
            <option :value="1">1</option>
            <option :value="2">2</option>
            <option :value="3">3</option>
        </select>

        <button @click="increment">+</button>
        <button @click="decrement">-</button>
        <button @click="incrementOdd">当前和为奇数时才加</button>
        <button @click="incrementWait">等一等再加</button>

    </div>

</template>

<script>
    export default {
        name: 'Count',
        data() {
            return {
                // 当前的和
                sum: 0,
                //  用户选择的数据
                n: 1
            }
        },
        methods: {
            increment() {
                this.sum += this.n
            },
            decrement() {
                if (this.sum > 0) {
                    this.sum -= this.n
                }
            },
            incrementOdd() {
                if (this.sum % 2 !== 0) {
                    this.sum += this.n
                }
            },
            incrementWait() {
                setTimeout(() => {
                    this.sum += this.n
                }, 1000)
            }
        }
    }

</script>

<style scoped>
    button {
        margin: 5px;
    }

</style>